Flexible bladed fan with strengthened leading edge

ABSTRACT

A flexible bladed automotive cooling fan having a reinforcing member on the upstream side of the blade, the reinforcing member radially spaced inwardly from the tip of the blade a distance in the range of 25-50 percent of the radial extent of the blade and the blade reversely bent continuously along its leading edge overlying the reinforcing member at an inner portion of the reverse bend.

nited States Patent [191 Strick Aug. 6, 1974 FLEXIBLE BLADED FAN WITH3,664,165 5/1972 Harvill et al. 416/240 UX STRENGTHENED LEADING EDGEInventor! Karl Chatham, Ontario, Primary Examine rEverette A. Powell,Jr.

Canada [73] Assignee: Foram Corporation, East Providence, RI. [57]ABSTRACT [22] Wed: 1973 A flexible bladed automotive cooling fan havinga re- [21] Appl. No.: 390,010 inforcing member on the upstream side ofthe blade, the reinforcing member radially spaced inwardly from g thetip of the blade a distance in the range of 25-50 g 1 6 3 percent of theradial extent of the blade and the blade [58] Fieid 136 A 240 reverselybent continuously along its leading edge v overlying the reinforcingmember at an inner portion [56] References Cited of the reverse bend.

UNITED STATES PATENTS Weir 416/132 4 Claims, 3 Drawing Figures FLEXIBLEBLADED FAN WITH STRENGTHENED LEADING EDGE BACKGROUND OF THE INVENTION 1.Field Of The Invention This invention relates to automotive fans andparticularly to automotive fans employing resilient blades whichdecamber as rotational fan speed increases.

2 Description Of The Prior Art Strength at the leading edge of a fanblade assembly, to prevent vibration, and minimal fan weight are basicdesign parameters with any automotive fan. Weight is important as,typically, the fan is mounted as a cantilevered load on the end of anengine water pump shaft and unnecessary weight is deleterious to waterpump shaft and bearing life. Vibration is a matter of concernparticularly at the outer tip of the fan blade as unnecessary vibrationcan lead to metal fatigue and premature blade failure. Vibrationtransmitted from the blade to an overlying reinforcing member can alsolead to fatigue and failure of the reinforcing member.

Heretofore, to deal with blade tip vibration, a reinforcing member ofheavier material than the blade was, in some fans, wrapped around theblade leading edge and extended along substantially the entire leadingedge thereof, as in US. Pat. No. 3,594,098. In other fans, a reinforcingmember was simply placed on the upstream side of the blade extendingalong substantially the entire leading edge thereof and was securedthereto by rivets including a rivet adjacent the blade tip, as in US.Pat. No. 3,594,098. In yet another design, as in US. Pat. No. 3,406,760,the reinforcing member comprised one or two reverse folds of the bladeupon itself extending along the entire leading edge of the blade andhaving a substantial transverse width for supporting and reinforcing theblade during decambering. In each of the foregoing fans, the reinforcingmember extending substantially along the entire length of the bladeleading edge contributes materially to overall fan 3 SUMMARY OF THEINVENTION In general the present invention features a reinforcing memberoverlying the fan blade and extending from the radially inner edge ofthe blade to a position spaced from the radially outer edge or tip ofthe blade a distance in the range of about 25-50 percent of the radialextent of the blade. The leading edge of the blade is reversely bentalong substantially its entire length and overlies the reinforcingmember thereadjacent. The reverse bend of the blade leading edgeprovides inherently increased strength and rigidity to the leading edgeof both the blade and the reinforcing member. Additionally, since thereverse bend overlies the reinforcing member, additional strength andresistance to bending stresses is provided to the blade leading edgeoutwardly of the reinforcing member by the transmission of forces to thereinforcing member. This in turn permits the use of the shortreinforcing member which reduces the weight of the fan. Since thereverse bend is not used for supporting the blade as it decambers, itneed not extend rearwardly any substantial distance and terminatesforward of fasteners connecting the blade and the reinforcing member.The reduction of material in the reinforcing member exceeds theadditional blade material employed in the reverse bend.

In a preferred embodiment, the reinforcing member comprises a memberseparate from the supporting arm. Also in a preferred embodiment theouter portion of the blade leading edge is more tightly folded outwardlyof the reinforcing member.

Advantageously, the fold of the blade leading edge provides strength toimprove durability in handling of the fan and contributes to personalsafety by turning back a relatively sharp blade edge. The elimination ofa tip rivet, employed in certain prior art fans, eliminates weight andeliminates, as well, a stress riser at the blade tip. The folded leadingedge also protects against the accumulation of foreign matter betweenthe blade and the reinforcing members, another potential source ofstress risers.

BRIEF DESCRIPTION OF THE DRAWING Other objects, features and advantagesof this invention will be apparent to those skilled in the art from thefollowing detailed description of a preferred embodiment thereof takentogether with the accompanying drawing, in which:

FIG. 1 is a fragmentary plan view of a fan embodying the invention;

FIG. 2 is an enlarged sectional view taken along the line 2-2 of FIG. 1;and

FIG. 3 is an enlarged fragmentary end view taken along the line 3--3 ofFIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT As illustrated in FIG. 1, thefan embodying the invention comprises a central hub 10 having aplurality of arms 12, integral with hub 10 and extending generallyradially outwardly from the hub 10.

Overlying each arm 12, on the upstream side thereof, defined by thedirection of airflow as indicated by arrows in FIG. 2, is mounted ablade 14 of thin flexible resilient material, AISI 301 stainless steel0.020 inch thick in the illustrated preferred embodiment. The blade 14has generally radially extending leading and trailing edges l6, 18,respectively defined by the direction of fan rotation indicated byarrows in FIG. I. The blade 14 is curved between the transversely spacedleading and trailing edges 16, 18 thereof, presenting a convex side onthe upstream side of the blade 14 and a concave side on the downstreamside thereof. The leading edge 16 is positioned forward of arm 12 andthe trailing edge 18 is positioned behind the arm 12.

Overlying blade 14, on the upstream side thereof, is a relatively rigidreinforcing member 26. Member 26 has a leading edge 28 adjacent bladeleading edge 16 and extends transversely to a trailing edge 30intermediate the blade leading and trailing edges l6, l8. Member 26extends radially along blade 14 from adjacent the inner edge 20 of blade14 to a position inwardly spaced from blade tip 22 a distance in therange of about 25-50 percent, about 30 percent in the illustratedpreferred embodiment, of the radial extent of the blade 14. A radiallyextending strengthening rib 32 is provided along member 26 rearwardly ofits leading edge 28.

Rivet fasteners 34 extend through and fasten together arm 12, blade 14and reinforcing member 26. Fasteners 34 are positioned rearwardly ofblade and reinforcing member leading edges 16, 28 and rearwardly of rib32.

The blade 14 is reversely bent at its leading edge to provide areversely bent portion 24 on the upstream side thereof. Reversely bentportion 24 extends continuously along substantially the entire length ofblade leading edge 16, the radially inner portion thereof overlyingreinforcing member 26 and the outer portion thereof overlying theupstream side of blade 14. The reversely bent portion 24 of blade 14extends rearwardly from blade leading edge 16 a limited extent to aposition forward of fasteners 34 and forward of reinforcing member rib32. As illustrated in FIG. 3, the outer portion of reversely bentportion 24 is bent to a position more closely adjacent the underlyingportion of blade 14 thereadjacent than is possible at the inner portionof reversely bent portion 24 overlying reinforcing member 26, thusassuring tight contact of the inner portion with reinforcing member 26.

In operation, the continuous reverse bend at the leading edge of blade14 inherently strengthens the blade leading edge to resist vibration.Overlying reinforcing member 26, additional resistance to vibration inuse is imparted to blade 14 beyond member 26. Advantageously, thereversely bent portion 24 overlying reinforcing member 26 alsorigidities and mutually strengthens member 26. Thus, a shorterreinforcing member 26 may be employed without inadmissably shorteningfatigue life of the blade and, additionally lighter material may beemployed in the reinforcing member 26 than heretofore customary, 0.060inch thick aluminum being used in the illustrated preferred embodiment.The result is a strenghtened leading edge in the fan blade assembly anda desirably lighter fan.

Other embodiments of this invention will occur to those skilled in theart which are within the scope of the following claims. ln one suchmodification, the reinforcing member may comprise an integral portion ofthe arm.

What is claimed is:

1. In an automotive cooling fan having a hub, arms radially projectingfrom said hub and blade structures connected to said arms, said bladestructures each comprising:

a resilient blade having generally radially extending,

transversely spaced leading and trailing edges, said blade extendingfrom its inner edge adjacent said hub to a blade tip remote from saidhub, said blade having one side facing upstream of the direction ofairflow and the other side facing downstream thereof, the portion ofsaid blade adjacent said trailing edge thereof decambering in anupstream direction as fan rotational speed increases;

a blade reinforcing member positioned against the upstream side of saidblade and having a leading edge adjacent said blade leading edge, saidreinforcing member extending transversely from adjacent said bladeleading edge in the direction of said blade trailing edge and extendinggenerally radially from adjacent said inner edge of said blade towardsaid tip thereof; and

a plurality of fasteners connecting said blade and said reinforcingmember, said fasteners spaced rearwardly from said blade and reinforcingmember leading edges;

the improvement in said blade structure in which said reinforcing memberextends generally radially from adjacent said inner edge of said bladeto a position spaced radially inwardly from said tip of said blade adistance in the range of about 25-50 percent of the radial extent ofsaid blade; and

said blade is continuously reversely bent along substantially the lengthof its said leading edge providing a radially inner reversely bentportion thereof bent around said reinforcing member leading edge andtransversely extending along the upstream side of said reinforcingmember a limited extent to a position intermediate said reinforcingmember leading edge and said fasteners and providing a radially outerreversely bent portion thereof extending radially outwardly of saidreinforcing member substantially to said blade tip, said inner and outerreversely bent portions integral with said blade and with each other.

2. The improvement claimed in claim 1 in which said outer reversely bentportion is bent to a position more closely adjacent the portion of saidblade which it overlies than said inner reversely bent portion.

3. The improvement claimed in claim 1 in which said blade andreinforcing member are positioned on the upstream side of one said armand are connected thereto by said fasteners.

4. The improvement claimed in claim 3 in which said outer reversely bentportion is bent to a position more closely adjacent the portion of saidblade which it overlies than said inner reversely bent portion.

UNITED STATES PATENT GFFICE CERTIFIECATE OF CGRREQTION Patent No. 3,827,826 I Dated August 6, 1974 Inventofls) Karl H. Strick v I It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Change the Ass ignee from "Foram Corporation" to "Pram Corporation-Signed and sealed this 3rd day of December 1974.

(SEAL) Attest:

McCOY M.. GIBSON JR'. 0. MARSHALL DANN Attesting Officer Commissioner ofPatents mm b mum; Hil 15)

1. In an automotive cooling fan having a hub, arms radially projectingfrom said hub and blade structures connected to said arms, said bladestructures each comprising: a resilient blade having generally radiallyextending, transversely spaced leading and trailing edges, said bladeextending from its inner edge adjacent said hub to a blade tip remotefrom said hub, said blade having one side facing upstream of thedirection of airflow and the other side facing downstream thereof, theportion of said blade adjacent said trailing edge thereof decambering inan upstream direction as fan rotational speed increases; a bladereinforcing member positioned against the upstream side of said bladeand having a leading edge adjacent said blade leading edge, saidreinforcing member extending transversely from adjacent said bladeleading edge in the direction of said blade trailing edge and extendinggenerally radially from adjacent said inner edge of said blade towardsaid tip thereof; and a plurality of fasteners connecting said blade andsaid reinforcing member, said fasteners spaced rearwardly from saidblade and reinforcing member leading edges; the improvement in saidblade structure in which said reinforcing member extends generallyradially from adjacent said inner edge of said blade to a positionspaced radially inwardly from said tip of said blade a distance in therange of about 25-50 percent of the radial extent of said blade; andsaid blade is continuously reversely bent along substantially the lengthof its said leading edge providing a radially inner reversely bentportion thereof bent around said reinforcing member leading edge andtransversely extending along the upstream side of said reinforcingmember a limited extent to a position intermediate said reinforcingmember leading edge and said fasteners and providing a radially outerreversely bent portion thereof extending radially outwardly of saidreinforcing member substantially to said blade tip, said inner and outerreversely bent portions integral with said blade and with each other. 2.The improvement claimed in claim 1 in which said outer reversely bentportion is bent to a position more closely adjacent the portion of saidblade which it overlies than said inner reversely bent portion.
 3. Theimprovement claimed in claim 1 in which said blade and reinforcingmember are positioned on the upstream side of one said arm and areconnected thereto by said fasteners.
 4. The improvement claimed in claim3 in which said outer reversely bent portion is bent to a position moreclosely adjacent the portion of said blade which it overlies than saidinner reversely bent portion.